The invention concerns an indicating device for the optical reproduction of graphics, with a data-processing installation for the graphic processing of the information to be represented and with an indicating unit for the visualization of the processed information, wherein the data-processing installation uses, among others, antialiasing procedures.
Objects which are synthetically generated and described symbolically by means of edges, contours and surfaces are represented as arrangements of discrete points on a matrix display, as a consequence of rastering the area of representation. Since the resolutive power achieved in, say, photography, has not as yet been possible in the field of generative graphics, there occur characteristic imaging faults (representational faults) which are subsumed in the designation aliasing effects or distortion. Typically these effects manifest themselves in the stepped appearance of lines and surface border which actually are smooth, between the structures in the original image and the raster grid of the screen. Other manifestations of aliasing include shifts and even complete losses of details, as well as changes in contours or, in animated images, the blinking of fine details.
There exist procedures for minimizing imaging faults and thus to enhance image quality. In general, these procedures are referred-to as antialiasing procedures or antialiasing algorithms.
In one procedure, the image is computed with a higher resolution than is subsequently displayed on the monitor. After computation, the image is reduced to the desired resolution by means of a digital filter; with this, the individual information-carrying pixels of the original image are summarized in weighted fashion. This reduces the aliasing effects, but is a very costly method, inasmuch as the number of computations involved increases in proportion to the square of the resolution of the matrix display. In this process the individual pixels are considered as discrete points in the mathematical sense.
In another procedure the image is pre-filtered, in an attempt to filter out the high frequencies. In this procedure one produces, as it were, an xe2x80x9cartificial lack of sharpness,xe2x80x9d which smudges the aliasing effects, thus diminishing them. This approach is equivalent to treating the individual pixels as elementary surfaces.
In yet another procedure, designed to reduce faults in scan timing, one generates a greater number of images than is necessary for a given sequence of images, in order to subsequently filter them together in weighted fashion, at the timed output rate. This will smudge the contours of moving objects (motion blur).
One improvement designed to suppress aliasing effects consists of raising the number of pixels per unit of area. However, this is accompanied by higher costs, due to more expensive matrix displays and to the additional costs of storage and computing. Specifically in the case of instrumentation and multifunction displays in automotive vehicles, indicating [display] devices used for the representation of digitalized monochrome or color images are small and of low resolution.
Since the instrumentation and multifunction indicating devices in automotive vehicles are increasingly required to display graphics (such as navigational maps) in addition to the normal standard instruments such as digital indicators and pointer instruments, the low graphic resolution levels of the indicators resulted in pronounced aliasing effects. Today, the instrumentation of automotive vehicles generally involves small indicating devices with up to 400,000 pixels. As a function of pixel size, apparatus, geometry and configuration, this yielded pronounced aliasing effects. For instance, the low level of resolution made it impossible to represent inclined letters in a distortion-free or even legible manner. Strong aliasing effects were also noticeable in the case of streets or other graphic objects represented by short lines. This greatly impairs the quality of the image and the informational content is hard to read out.
Because of the costs of high-resolution displays, there is increasing use of antialiasing techniques in order to enhance the virtual resolution of monitors and displays. However, since this places considerable demand on computing capacity, one generally has to pay a corresponding price in image-processing time, unless one uses a graphic accelerator, capable of high-speed antialiasing algorithms via appropriate circuitry.
It is the task of the present invention to offer an indicating device in which image quality is improved by the use of antialiasing procedures, while also fulfilling the requirements for high frame update rates, so as to produce as much as possible a non-jolting or smooth image.
According to the invention, this task is accomplished in that, when generating an image, the data-processing installation utilizesxe2x80x94in the graphic processing of at least two image areas or image objects of the imagexe2x80x94different antialiasing procedures for these image areas or image objects; or else represents one image area or image object without an antialiasing procedure. By adopting such a procedure in the generation of an image, one can, for instance, represent objects that move relatively slowly over time with an antialiasing procedure which permits a higher image quality for such an image area or such an image object. On the other hand, fast-moving image objects, or image areas in which the objects move quickly, may be represented with an antialiasing procedure that is less computation-intensivexe2x80x94or else, without any antialiasing procedure at all. By adopting this compromise, an advantageous saving in computational capacity is achieved, so that in spite of improved image quality a high frame update rate is reached (or the number of newly computed images per second remains relatively high).
The same advantage is provided by a solution according to the invention in whichxe2x80x94as a function of the available computing capacity of the data-processing installation, and/or of the frame repetition rate, and/or of the number of objects to be representedxe2x80x94different antialiasing procedures are utilized in the generation of images to be represented sequentially. In this solution, the data-processing installation determines in each case the time span required for the representation of the object to be represented, by various antialiasing procedures; it then determines whether the computing capacity and the time which results from the required frame repetition rate are sufficient to represent the image, using a given antialiasing procedure. If the time is not sufficient for representing the image produced via a specific antialiasing procedure, a less computation-intensive antialiasing procedure will have to be selected for the representation of that image. In this case one can store a table in the data-processing installation, in which table it can be read off directly whether or not a specific number of image objects can be represented or computed in a specific time span, with a specific antialiasing procedure.
Obviously the two solutions mentioned above can be combined; this results in a variety of possibilities of image processing or representation, allowing optimum utilization of the available hardware.
It is also advantageous in the generation of an image to keep on utilizing a computation-intensive antialiasing procedure for the representation of individual image areas and/or objects until the request for a new frame update is generated, after which the remaining image areas or objects to be represented are not represented at all, or are represented with a less computation-intensive antialiasing procedure. Particularly in indicating devices in vehicles it may occur that, because of a change in the situation, a rapid change in images may suddenly become necessary. In order to nonetheless represent in the display all the objects not as yet drawn, it is possible to obtain a gain in time by replacing the antialiasing procedure heretofore used for the momentary image construction by a less computation-intensive procedure or algorithm, thus speeding up the remaining image construction.
It also is advantageous if one can predetermine which antialiasing procedure is to be used by the data-processing installation for which image area. Naturally it is also possible to represent an image area or an image object without an antialiasing procedure. Thus one can represent on the matrix display an analog clock with pointers, using a computation-intensive antialiasing procedure. On the other hand, the navigational mapxe2x80x94also represented on the same matrix displayxe2x80x94is represented with a less computation-intensive antialiasing procedure, since, at high vehicle speed and frequent changes in direction, the objects on the map will generally move more rapidly than the pointers of the analog clock. For instance, using that procedure while the vehicle moves at lower speed, one could also represent the navigational map by means of a computation-intensive antialiasing procedure, inasmuch as the number of images per second to be newly computed at low speeds is smaller.
The following antialiasing procedures are imaginable. For one thing, if the computing capacity is very low or the graphics change very rapidly, it is possible to use no antialiasing procedure at allxe2x80x94i.e., lines and contours are represented solely by means of standard algorithms and are not further processed. The greater the available computing capacity and/or time, the more computation-intensive can be the antialiasing algorithm utilized.
This essential part of the invention may be called xe2x80x9cscaled antialiasing.xe2x80x9d The individual steps are listed in order of increasing computing intensity in claim 8.
Below, the invention is explained in greater detail on the basis of figures.